Gas chromatography is commonly used in analytic chemistry for separating and analyzing compounds of a sample. For example, a gas chromatograph may be used to test the purity of a sample, identify a compound, separate different components of a mixture or to prepare (e.g., purify) compounds from a mixture. Gas chromatography is essentially a physical method of separation in which constituents of a test sample in a carrier gas are adsorbed and desorbed by a stationary phase material in a column. A pulse of the sample is injected into a steady flow of carrier gas. At the end of the column the individual components are more or less separated in time. Detection of the gas provides a time-scaled pattern which, by calibration or comparison with known samples, indicates the constituents of the test sample. The main components of such a system are the column, an injector for introducing the sample into carrier gas and passing the mixture into the column, a device for transferring sample into the injector, a detector at the outer end of the column, gas controls, and a device such as a computer for treating and displaying the output of the detector. An oven may be used to elevate temperature to maintain the sample in a volatile state, and to improve the discrimination of constituents.